What is the difference between an atomic bomb and a hydrogen bomb?

The fundamental difference between an atomic bomb and a hydrogen bomb lies in the physical process used to generate their explosive energy.

• Atomic Bomb: These weapons rely on nuclear fission, a process in which the nucleus of a heavy atom, such as uranium or plutonium, splits into lighter elements when bombarded by neutrons. This splitting releases significant energy and additional neutrons, sustaining a chain reaction.12
• Hydrogen Bomb: Also known as a thermonuclear bomb, this weapon utilizes nuclear fusion. In this process, isotopes of hydrogen combine at extremely high temperatures to form helium. Because these high temperatures are required to initiate fusion, a hydrogen bomb actually uses a small atomic bomb as a "primary" stage to trigger the fusion reaction.234

While atomic bomb yields are typically measured in kilotons, hydrogen bombs can be hundreds or thousands of times more powerful, with yields often expressed in megatons.2